In turn, these commodities traders provide a significant portion of revenues for governments of African oil-producing countries. But weak institutions and widespread corruption in many of these producer nations mean these transactions come under little scrutiny, says the report.

The NGOs want to know more. Indeed, without better disclosure, they reckon the lack of information leaves “a black hole” in the transparency of the global resources market.

“These oil fields are the biggest revenue streams in several countries and they’re treated like these niche, technical things only a few people should be aware of,” said Alexandra Gillies head of governance at the Natural Resource Governance Institute and one of the report’s authors. “The risks are very high and I think unacceptably high,” she said.

The report comes as regulators around the world have been waking up to the important role played by mostly-private traders in moving commodities around the world.

The U.K.’s Financial Conduct Authority called commodities traders a “known unknown” in a February report and wants a closer dialog with them. Even Switzerland’s Federal Council is considering the issue.

Trading companies argue they are already covered by a whole host of regulations and that mandatory reporting of all their trades would not only be very burdensome, but also generate huge volumes of data. They also don’t like the idea of revealing trade secrets to their competitors.

One thing on the traders’ side is that it would likely need a co-ordinated international effort to force them into disclosing more.

The Swiss government says it will only implement rules requiring the commodity trading industry to disclose their payments to foreign governments if the U.S. and EU introduced similar legislation.

The traders themselves don’t seem to be holding their breath for that.

“This agenda is complex, global and multi-faceted and would require many parties including producing governments to agree before any new regime could be introduced,” said Singapore-based trading company Trafigura Beheer B.V. in a statement responding to the report.

Glencore declined to comment on the report but said it is committed to full compliance with all its statutory obligations to tax authorities and to reporting transparently on its tax payments to governments in the countries in which it operates.